Primary intrahepatic malignant mesothelioma of epithelioid type

A case of epithelioid mesothelioma presenting as a primary intrahepatic tumor is described. The patient was a 62-year-old man with a 5.8-cm intrahepatic mass on an incidental intra-abdominal CT scan. Thorough clinical and radiographic examination did not reveal any evidence of tumor elsewhere. Macroscopic and microscopic examination demonstrated an intrahepatic tumor consisting of tubular and papillary proliferations of large epithelioid cells, surrounded by a densely mixed inflammatory infiltrate. The tumor cells were strongly positive for pancytokeratin, CK7, CA-12.5, and calretinin, as well as D2-40, and were faintly positive for thrombomodulin and vimentin. The proliferative rate was focally increased up to 20% by Ki-67 staining and the tumor expressed focally p53. Ultrastructurally, numerous microvilli on the cell surface, and abundant desmosomal plaques, characteristic of mesothelial cells, were found. To date, this is the third reported case of a primary intrahepatic mesothelioma.